Hydraulic Cylinder Thread-Weld Coupling for Thinner Tube Walls
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Solution Overview
Problem
Existing hydraulic working cylinders require increased material thickness for thread machining, leading to oversized tube wall thickness, increased material consumption, and higher final weight, while also necessitating longer thread lengths to absorb axial forces, which can be disadvantageous in certain installation situations.
Innovation Solution
The working cylinder features a specially designed coupling between the cylinder tube and closure parts, utilizing a common threaded portion and a ring weld seam for axial force absorption, with the ring weld seam absorbing axial tensile forces during low operating pressure and both the ring weld seam and common threaded portion absorbing forces during high operating pressure, thereby reducing the stress on the common threaded portion and allowing for thinner-walled cylinder tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cylinder tube wall thickness is increased to accommodate thread machining, then the thread can be machined in a subtractive process, but the material consumption and final weight increase significantly
Solution Approach 1:
The coupling between cylinder tube and closure part is segmented into two functional zones: a welded zone for substance-locking connection and a threaded zone for form-fit connection. This segmentation allows the threaded portion to be shorter and located only where needed for force transmission, reducing the overall material requirement while maintaining both manufacturability and structural integrity
Solution Approach 2:
The invention merges two connection methods (welding and threading) into a single coupled design where the closure part is both welded to and threaded into the cylinder tube. This combination allows the threaded portion to be optimized for minimal length while the welded portion provides the primary structural connection, reducing material consumption compared to pure threading
2Strength
If a longer thread length is provided to absorb axial forces, then the high axial forces from operating pressure and pre-stress can be absorbed, but the length dimensions of the cylinder increase
Solution Approach 1:
The force absorption function is segmented between two connection mechanisms: the welded connection handles the primary axial force transmission, while the threaded connection provides supplementary force absorption and positioning. This segmentation allows the threaded portion to be significantly shorter while maintaining adequate axial force absorption capability
Solution Approach 2:
The welded connection acts as an intermediary that transfers axial forces directly between the closure part and cylinder tube, reducing the burden on the threaded connection. This mediator approach allows the threaded portion to be optimized for minimal length while the welded portion handles the majority of force transmission
3Ease of manufacture
If the cylinder tube wall thickness is increased, then the thread can be machined subtractively, but the tube wall thickness becomes oversized for absorbing forces during operation
Solution Approach 1:
The connection design segments the force absorption function from the thread machining function. The welded portion provides the primary structural strength for force absorption, while the threaded portion is optimized only for the minimal material needed to accommodate the threading process and provide form-fit connection
Solution Approach 2:
The cylinder tube exhibits local quality variation where the wall thickness is optimized differently for different functions: the welded zone provides thick-walled structural strength for force absorption, while the threaded zone has minimal wall thickness sufficient only for thread formation and connection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the axial tensile force absorbed by the common threaded portion, allowing for a shorter threaded portion and thinner cylinder tube walls, resulting in material savings, reduced machining time, and smaller cylinder sizes with the same stroke, while also distributing force effectively to prevent overloading of the ring weld seam.
Implementation Method 1
the intermediate cylinder tube portion (5.2a) is designed for axial strain within its elasticity limit when the operating state under load relief changes to the operating state under load
Implementation Method 2
carrying out laser welding of the cylinder tube end and the closure part
Data Source
AI summary
A working cylinder has a cylinder with a cylinder tube, and a piston unit, The cylinder has a coupling portion which has a closure part and cylinder tube end portion that has a threaded cylinder tube portion, a cylinder tube intermediate portion and a cylinder tube end. The closure part has an external thread and the threaded cylinder tube portion has an internal thread corresponding to the external thread. The external thread and the internal thread define a common threaded portion which is couples the closure part and the cylinder tube with a form fit. The cylinder tube end is connected to the closure part by a circumferential ring weld seam configured as a laser-produced ring weld seam and defines a sealing plane which is tight to pressure medium. In an operating state under load alleviation, the common threaded portion does not absorb an axial tensile force, and in the operating state under load, the ring weld seam and the common threaded portion each absorb an axial tensile force. There is a method for the production of the cylinder.